CN1668445B - Method for manufacturing thermoplastic resin container - Google Patents

Abstract

The invention relates to a method for manufacturing a thermoplastic resin container, which is a method for heating and forming a cup-shaped container from a thermoplastic resin sheet by a male die, wherein the periphery of a forming part of the thermoplastic resin sheet is fixed by a pre-clamping metal die, and then the thermoplastic resin sheet is preformed by the male die; then, the preformed part of the thermoplastic resin sheet is stretched and formed by a male die in a state of being clamped by an upper die and a lower die, and then compressed air is formed into the shape of the inner surface of the lower die heated to the crystallization temperature of the thermoplastic resin sheet or higher, and simultaneously heat fixation is carried out; then, the inside of the molded body is decompressed and contracted, and is shaped into the shape of a male mold which is the shape of the final container, and is cooled; by this manufacturing method, the container bottom can be thickened and the warpage of the flange can be improved.

Description

Manufacturing method of thermoplastic resin container

technical field

The present invention relates to a method of manufacturing a container obtained by thermoforming a thermoplastic resin sheet, in particular, a method of manufacturing a container which thickens the bottom of the container and prevents warping of the flange.

current technology

Demand for thermoplastic resin containers is expected to increase in the future due to their excellent impact resistance and ease of use. In particular, thermoplastic polyesters such as polyethylene terephthalate have excellent impact resistance, excellent transparency, and gas barrier properties, and are widely used in various containers.

Such thermoplastic resin containers include, for example, flanged containers formed by thermoforming stretched or unstretched thermoplastic resin sheets.

As a method of manufacturing such a container, for example, there is a softened polyethylene terephthalate sheet, which is heated to a metal female mold above the glass transition point of the sheet, and a male mold is used to compress and expand it, contact it, and heat it. After the shape is set, it shrinks back on the male mold and cools, thereby making a method (Japanese Patent, Japanese Patent Application Publication No. 58-89319).

With this molding method, since the polyethylene terephthalate sheet is stretched, transparency can be imparted. Moreover, heat resistance can be improved by heat setting.

However, in this manufacturing method, the bottom of the container is overstretched to thin the bottom and its surroundings, and there is a problem that forming is difficult especially when deep-drawing containers are manufactured.

In addition, there was also a problem of warping upward in the flange portion of the manufactured container.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a method for manufacturing a thermoplastic resin container that increases the thickness of the bottom of the container and improves the warpage of the flange portion.

In order to solve the above-mentioned problems, the present inventors conducted intensive studies and found that: in the process of forming a thermoplastic resin sheet into a container using a male mold, firstly, the outer periphery of the molded part of the thermoplastic resin sheet is fixed by a pre-clamped metal mold and then fixed with a male mold. The above-mentioned thermoplastic resin sheet is preformed by the mold, and then the preformed part of the above-mentioned thermoplastic resin sheet is clamped by the upper metal mold and the lower metal mold, and then the male mold is inserted into the sheet to the end of the stroke to carry out the formal forming of the container body (stretching) Forming) can thicken the bottom of the container and improve the warpage of the flange, thus completing the present invention.

Contents of the invention

The manufacturing method of the thermoplastic resin container of the present invention is that in the method of thermoforming a cup-shaped container from a thermoplastic resin sheet with a male mold, after fixing the outer periphery of the molding part of the above-mentioned thermoplastic resin sheet with a pre-clamped metal mold, the above-mentioned The above-mentioned thermoplastic resin sheet is preformed by the male mold; then, the preformed part of the above-mentioned thermoplastic resin sheet is stretch-formed by the above-mentioned male mold in a state sandwiched by the upper metal mold and the lower metal mold, and compressed air is formed into The shape of the inner surface of the lower metal mold heated to a temperature above the crystallization temperature of the thermoplastic resin sheet is simultaneously heat-fixed; then, the molded body is depressurized and shrunk to form the shape of the male mold as the final shape of the container. shape while cooling.

The clamping process can be carried out between the preforming and the main forming (forming without stopping the male die), or after the preforming is completed (when the male die is stopped once).

In addition, the temperature of the above-mentioned pre-clamped metal mold is cooled to be lower than the glass transition temperature of the thermoplastic resin sheet or lower than the softening point.

In addition, the resin sheet does not need to be stretched by preforming, but it is preferable that the portion corresponding to the opening or the flange of the resin sheet container is stretched by preforming.

In this way, by preforming the portion corresponding to the opening of the container, the orientation of the opening is crystallized, and warpage after forming can be improved. In addition, by stretching the portion corresponding to the opening of the container before the container body is formed, resin can be introduced into the container side from the portion that has been treated as a skeleton in the past. Therefore, the bottom of the container can be thickened.

In addition, the thermoforming method uses compressed air to form a thermoplastic resin sheet into the shape of a lower metal mold heated to a temperature above the crystallization temperature of the thermoplastic resin sheet, heat-setting at the same time, and then depressurizes the molded body to shrink it to give Forming the above-mentioned positive mold shape into the final container shape, while cooling the molding method, the mechanical strength, transparency, and heat resistance of the thermoplastic polyester resin are improved.

In this specification, the term "opening" refers to the opening and its surroundings.

The manufacturing method of the present invention is particularly suitable for the manufacture of flanged cup-shaped containers. That is: the manufacturing method of the thermoplastic resin container of the present invention, its step is in the cup-shaped container method of thermoforming band flange with male mold from thermoplastic resin sheet, at first carry out the preforming of the part corresponding to above-mentioned flange part, from The resin is introduced into the part corresponding to the flange part and/or its outer periphery. After the above-mentioned preforming, the above-mentioned stretched part of the thermoplastic resin sheet is clamped, and a part of the resin corresponding to the flange part is directed to the inner periphery of the flange and While extruding in the peripheral direction, the flange portion is formed.

In this way, the orientation of the flange portion is crystallized, and warpage after molding can be improved. In addition, before the main body of the container is fully formed, by preforming and stretching the part corresponding to the flange part, resin can be introduced into the container side from the part that has been treated as the frame in the past, and the bottom of the container can be thickened. Moreover, when forming the flange portion, the resin flows from the portion corresponding to the flange portion of the clamped sheet to the inside of the flange portion (inner peripheral direction) and the outside of the flange portion (outer peripheral direction). Flow orientation occurs in the flange portion, and orientation crystallization is promoted, thereby improving warpage after molding.

In this specification, a flange part means a flange part and its surroundings.

In the present invention, it is preferable to include a step of fixing the outer periphery of the formed portion, that is, the outer periphery of the portion corresponding to the container opening or the flange portion (hereinafter referred to as the pre-clamping step) during preforming with the male mold.

For example, when a plurality of containers are simultaneously formed from one sheet, a die apparatus 90 in which a plurality of forming dies 91 are arranged adjacent to each other as shown in FIG. 11 can be used. At this time, connection of resin sheets occurs between adjacent dies during molding. Moreover, even if it is a specific metal mold, the distance between the surrounding metal mold 91 or the frame 92 will be different, and the amount of resin between them will also be different, so that errors will occur in the amount of resin introduced, and the container There is a problem of variation in the wall thickness between containers and the container itself.

From such a viewpoint, the manufacturing method of the thermoplastic resin container of this invention has the process of pre-clamping the outer periphery of a preformed part, ie, the outer periphery of the part corresponding to an opening part or a flange part.

With such a pre-clamping process, it is possible to prevent the connection of the resin sheets between the metal molds. In addition, the difference in the amount of introduced resin due to the arrangement of the metal mold can be eliminated, and the uniformity of the wall thickness and weight of the container can be achieved.

Alternatively, it is also possible to partially control the wall thickness of the container by conversely providing an arbitrary difference in the distance between the die and the pre-clamp.

In addition, in the present invention, the thermoplastic resin sheet is preferably coated with a lubricant such as silicone oil, palm oil, or vegetable oil such as gramawax at least on the portion corresponding to the flange portion. To reduce the impact on the contents, it can also be coated only on the surface.

In this way, scratches on the outer surface of the side wall generated under the flange due to friction between the lower mold and the sheet when the sheet is clamped for forming the flange portion can be reduced. In addition, since a portion of the clamped portion is crushed, a part of the resin is extruded from the portion and easily flows to the inside and outside of the flange portion, so the flow orientation of the resin at the clamped flange portion becomes conspicuous, Oriented crystallization is promoted, and warping of the flange portion can be prevented.

In the present invention, the thermoplastic resin sheet preferably consists of at least thermoplastic polyester resin. The thermoplastic resin sheet may be a single layer of thermoplastic polyester resin, or may be multiple layers of other resins containing polyester resin.

In this way, the thermoplastic polyester resin undergoes a stretching process and a heat setting (heat setting) process, and by orientation crystallization and thermal crystallization, mechanical strength, transparency, and heat resistance are improved.

In the present invention, the pre-clamping metal mold is provided with an upper pre-clamping metal mold coaxially arranged on the outer periphery of the upper metal mold, and a lower pre-clamping metal mold coaxially arranged on the outer periphery of the lower metal mold, and A thermoplastic resin sheet is clamped around the upper and lower metal molds.

In the present invention, it is preferable to shape the cup-shaped container so that H/D (height/opening diameter) is 1.3 to 2.1.

In the present invention, part of the resin that has not been used in the container can be used, so the bottom of the container can be thickened. However, if it is less than 1.3, the stretching will be insufficient, orientation crystallization may not be possible, and the transparency of the container may be lowered, and if it is greater than 2.1, shaping may become difficult. The ideal is between 1.3 and 1.8. That is, it is suitable for the manufacture of deep-drawn containers.

In the present invention, it is preferable to set the area draw ratio of the bottom of the container at 3.5 to 10 times. The most ideal is 3.5 to 9 times.

However, if it is less than 3.5 times, the orientation stretching will be insufficient, the transparency will decrease, and it will become brittle; if it exceeds 10 times, the strength will decrease due to thinning, and at the same time, the resin will harden due to excessive orientation crystallization. May cause difficulty in shaping.

Description of drawings

Fig. 1 is a side sectional view of a molding apparatus for carrying out the manufacturing method of the present invention.

Fig. 2 is a side sectional view when a thermoplastic resin sheet is fixed (pre-clamped).

Fig. 3 is a side sectional view showing a preforming step.

Fig. 4 is a side sectional view showing a molding step after sandwiching stretched portions of a thermoplastic resin sheet.

Fig. 5 is a side sectional view showing a stretching step.

Fig. 6 is a side sectional view showing a heat setting step.

Fig. 7 is a side sectional view showing cooling and forming steps.

Fig. 8 is a side sectional view showing a demolding step.

Fig. 9 is a plan view of a forming device for manufacturing a container having an oval cross-sectional shape.

Fig. 10 is a plan view of a forming apparatus for manufacturing a container having a square cross-sectional shape.

Fig. 11 is a plan view for explaining the positional relationship of male dies when a plurality of moldings are performed.

Detailed ways

Hereinafter, one embodiment of the production method of the present invention will be described. However, the present invention is not limited to this embodiment. 1 to 10 are drawings illustrating an embodiment in which the production method of the present invention is applied to a solid-phase molding method.

FIG. 1 is a schematic side sectional view of an example of a solid-phase forming apparatus for carrying out the production method of this embodiment.

The forming device 1 is mainly composed of a male mold 11 , a lower metal mold 12 , an upper metal mold 13 , an upper pre-clamping metal mold 14 and a lower pre-clamping metal mold 15 .

The male mold 11 is used to stretch and form the thermoplastic resin sheet 16, and shrinks and shapes the stretched and heat-set (heat-fixed) sheet so that it has the shape of the final molded body. The male mold 11 is provided with an air passage 111 for supplying compressed air and reducing pressure in the axial direction.

The lower metal mold 12 is a part for heat-setting the sheet that is separated from the male mold. On the upper end surface of the lower die 12, a flange clamping surface 122 for forming a flange portion in cooperation with the upper die 13 is provided. Also, a gas passage 121 for gas discharge and supply is formed at the center portion of the lower metal mold 12 .

The lower metal mold 12 and the male mold 11 are arranged coaxially, and can move relative to each other in the axial direction, so that the male mold 11 is inserted and isolated in the lower metal mold 12 .

The upper die 13 forms a flange portion (opening portion) in cooperation with the lower die 12 and is a hollow short cylindrical body. Therefore, the upper mold 13 has an inner surface 131 having substantially the same diameter as the cylindrical inner surface of the lower mold 12 and a clamping surface 132 having the same shape as the flange clamping surface 122 of the lower mold 12 on its lower end surface. In addition, the flange clamping surfaces of the above-mentioned upper and lower metal molds may be flat, and unevenness may be provided on one or both of the metal molds as required.

The upper pre-clamping metal mold 14 and the lower pre-clamping metal mold 15 are coaxially arranged on the outer peripheries of the upper metal mold 13 and the lower metal mold 12, and cooperate to fix the thermoplastic resin sheet. In addition, the lower pre-clamping die 15 operates independently of the male die 11 and the lower die 12 .

Next, the container manufacturing method of this embodiment will be specifically described. As shown in FIG. 1 , four sides or two sides of the sheet 16 are clamped (not shown in the figure), and fixed between the upper metal mold 13 and the lower metal mold 12 .

The temperature of the sheet at this time depends on the resin used. However, flakes of polyester resin have a glass transition point (Tg) to (Tg+45)°C. If the temperature of the sheet is higher than (Tg+45)°C, orientational crystallization cannot fully occur, and whitening caused by heating crystallization may occur in the heat setting process described later; if it is lower than Tg°C, not only High molding force is required, and molding itself is difficult, and the resin is in an overstretched state during molding, which may cause whitening.

FIG. 2 is a side sectional view of the thermoplastic resin sheet 16 pre-clamped by using the upper pre-clamping metal mold 14 and the lower pre-clamping metal mold 15 .

By clamping the sheet around the forming metal die, the relationship between the inside (pre-clamping area) and the outside of the clamped portion of the sheet can be insulated. Therefore, in the so-called multi-molding manufacturing in which a plurality of containers are formed from one sheet at a time, it is not affected by the influence of other clamping areas and the influence of the gap between the dies. In this way, containers having uniform quality (wall thickness, weight, etc.) can be obtained even when containers are produced by multiple moldings.

In addition, when manufacturing one container (one molding) from one sheet, as mentioned above, the four sides or two sides of the sheet 16 are generally clamped by the frame, so when using a sheet (size) that affects, it is best to carry out pre-clamped. However, the pre-clamping process can be omitted when the sheet size used is much larger than the container to be formed.

The temperature of the pre-clamping metal mold is preferably below the softening point or melting point of the sheet resin, and it may be cooled if necessary. By cooling the pre-clamped metal mold, deformation of the container due to thermal deformation of the sheet when the sheet is solidified after the demoulding process can be suppressed.

As the temperature of the pre-clamping mold, when the sheet is substantially amorphous or low-crystalline like polyester resin, it is preferable to cool the pre-clamping mold to below the glass transition temperature of the resin. On the other hand, when the sheet is obtained substantially by crystallization like polypropylene, it is preferable to cool the pre-clamping mold to below the softening point of the resin.

Here, the clamping surface for pre-clamping can be flat, or can be set in the shape of thin strips, concave-convex and other ribs. When it is set in the form of ribs, the thin sheet can be given rigidity after punching, and the same effect as that after cooling the pre-clamped metal mold can be obtained.

Fig. 3 is a side sectional view showing a step of stretching a portion corresponding to the opening or flange of the container and introducing resin from the outer periphery of the opening (preforming step).

The male die 11 presses the sheet 16 downward by a predetermined amount. In this way, the portion where the flange portion (opening portion) is formed is stretched in a later process. Therefore, the flange portion is crystallized due to orientation, and warpage after shaping can be prevented.

In addition, by this stretching, the resin is introduced from the outer periphery of the portion forming the opening or the flange of the container to the region inside the opening or the flange (molding region). In this way, the resin in the opening portion of the container or the outer peripheral portion of the flange portion that has not been used in the container can be effectively used, and the wall thickness of the bottom of the container can be increased.

At this time, the temperature of the male mold 11 is, for example, 70°C to 110°C in the case of a polyester resin sheet, preferably 80°C to 100°C.

The pressing amount (preforming amount) of the male mold 11 can be appropriately adjusted in consideration of the shape (wall thickness, height, bottom area, etc.) of the container to be manufactured, the pre-clamped area, and the thickness of the resin sheet.

When the amount of travel is insufficient, the stretching is insufficient, and the improvement of the warpage of the flange portion cannot be achieved. In addition, the introduction of resin is insufficient, and there is a possibility that the bottom of the manufactured container cannot be thickened.

On the other hand, if the amount of pre-molding is too large, the amount of resin introduced is too much, and the entire container, especially the resin at the bottom of the container, cannot be fully stretched in the stretching process using the male mold described later. The container cannot obtain sufficient orientation crystallization, and whitening may occur at the bottom.

Fig. 4 is a side sectional view showing a step of forming after sandwiching stretched portions of a thermoplastic resin sheet.

In this step, the lower mold 12 rises, and in cooperation with the upper mold 13, the flange portion (opening portion) is clamped by the respective clamping surfaces 122, 132 and formed. The flange portion is flow oriented by being clamped by the upper mold 13 and the lower mold 12 . At this time, if the thermoplastic resin sheet is coated with a lubricant such as silicone oil, palm oil, and vegetable oil such as Grammar wax at least on the portion corresponding to the flange portion, the inner corner of the clamping surface 122 and the sheet can be The gaps are smoothed to reduce scarring of the outer surface of the sidewall that occurs under the flange. In addition, when the clamped part is crushed and a part of the resin is extruded from the part, it is easy to flow into the inside and outside of the flange part, so the flow orientation of the resin in the clamped flange part becomes obvious, which promotes Orientation crystallization further improves the warpage of the flange portion.

At this time, the temperature of the upper mold is preferably room temperature to 150°C, more preferably 50°C to 130°C for the polyester resin sheet.

Fig. 5 is a side sectional view showing a stretching step when forming a container body.

In this step, the male die 11 is inserted into the lower die 12 to the end of the stroke, and the sheet 16 is stretched to perform oriented crystallization.

Fig. 6 is a side sectional view showing a heat setting step.

In this step, compressed air is supplied through the air passage 111 of the male mold 11 to bring the sheet 16 into contact with the inner surface of the lower mold 12 . At this time, the lower metal mold 12 is heated so that heat is applied to the sheet for heat setting. Moreover, at this time, air can also be sucked from the gas passage 121 of the lower metal mold 12, so that the thin sheet and the lower metal mold 12 can be more closely adhered, and heat setting can be effectively performed.

The temperature of the lower mold 12 during heat setting is preferably 120°C to 200°C, more preferably 140°C to 180°C for the polyester resin sheet.

When heat setting is not performed, the temperature of the metal mold may be adjusted to be below the glass transition temperature, and the mold may be cooled and shaped in a state of closely adhering to the metal mold, and then taken out as a final container.

Fig. 7 is a side sectional view showing cooling and forming steps.

In this step, the compressed air supplied from the passage 111 of the male mold 11 is stopped to cause the sheet to self-shrink. At the same time, air is sucked through the gas channel 111 to form a vacuum between the sheet and the male mold, and the sheet is formed into the shape of the outer surface of the male mold 11 . At this time, compressed air may be supplied from the gas passage 121 of the lower mold 12, so that the adhesion is better and the formability is improved.

Fig. 8 is a side sectional view showing a demolding step.

In this step, the metal mold and the preliminary clamping mold are opened, the male mold 11 is raised, and the final molded body is taken out.

The container production method of the present invention is suitable for the production of a container with a planar cross section, and is also suitable for the production of an oval-shaped container as shown in FIG. 9 or a square-shaped container as shown in FIG. 10 .

Fig. 9 is a plan view of a forming apparatus for manufacturing a container having an elliptical cross-sectional shape.

Fig. 10 is a plan view of a forming apparatus for manufacturing a container having a square cross-sectional shape.

That is, in the pre-clamping process, by adjusting the shape of the pre-clamping region, the wall thickness distribution of the container is controlled.

For example, when manufacturing a container with a circular planar cross-section, the pre-clamping region may need to have a shape similar to the flange inner end of the cup-shaped container when uniforming the wall thickness and weight of the container as described above.

On the other hand, when manufacturing a container with an ellipse in planar cross-section, a large amount of resin is introduced into the part with a large curvature where the wall thickness of the container is likely to become thinner, and the resin is passed between the inner end of the flange of the cup-shaped container and the pre-clamping area. By enlarging the spacing, the wall thickness distribution can be controlled.

In addition, when manufacturing a container with a square-shaped planar cross-section in which the wall thickness of the side is easy to become thin, as shown in FIG. By zooming in, the wall thickness distribution can be controlled.

In addition, in a container having a square shape in plan, the space between the inner end of the flange of the cup-shaped container and the pre-clamping area is placed larger at the long side than at the short side.

Furthermore, when the flake exhibits mechanical anisotropy due to molecular orientation, etc., the wall thickness distribution can be controlled by adjusting the pre-clamp region taking this factor into account.

The container manufacturing method of the present invention can be applied to sheets made of crystalline resins such as polyolefin resins such as polyethylene, polypropylene, and polystyrene, polyamide resins such as polyamide 6, polyamide 66, and polyamide 46. Polyester-based resins such as polyethylene terephthalate (PET), polybutylene terephthalate, polycarbonate, polyarylate resins, and amorphous resins such as cycloolefin-based copolymers slices of any kind. The above-mentioned sheet is not only a single-layer sheet but also a multi-layer sheet.

Specifically, it is preferable to use a polyester-based resin sheet having at least one polyester layer.

As the polyester used, it is a polyester derived from a hydroxy acid component mainly composed of an aromatic dihydroxy acid and an alcohol component mainly composed of an aliphatic dihydric alcohol. Preferably, 50 mol% or more of the hydroxy acid component is composed of A polyester composed of a terephthalic acid component and 50 mol% or more of an alcohol component is composed of an ethylene glycol component.

As long as the above conditions are met, the polyester may be homopolyester, copolyester or a mixture of two or more of the above.

Carboxylic acid components other than terephthalic acid components include: isophthalic acid, naphthalene dicarboxylic acid, P-β-hydroxyethoxybenzoic acid, biphenyl-4,4'-dicarboxylic acid, diphenoxy Ethane-4,4'-dicarboxylic acid, 5-sodiumsulfoisophthalic acid, hexahydroterephthalic acid, adipic acid, sebacic acid, trimellitic acid, pyromellitic acid, etc.

Alcohol components other than ethylene glycol include: 1,4-butanediol, propylene glycol, pentaerythiol, 1,6-hexenediol, diethylene glycol, triethylene glycol, cyclohexanedimethanol, Alcohol components such as ethylene oxide addenda of bisphenol A, glycerol, trimethylolpropane, pentaerythritol, dipentaerythritol, and sorbitan.

The best thermal polyester is polyethylene terephthalate, and other suitable ones include: polyethylene/butylene terephthalate, polyethylene terephthalate/2,6-naphthalene di Formate, polyethylene terephthalate/isophthalate and the aforementioned polyesters and polybutylene terephthalate, polybutylene terephthalate/isophthalate, poly Ethylene-2,6-naphthalate, polybutylene terephthalate/adipate, polyethylene-2,6-naphthalate/isophthalate, polyethylene terephthalate Butylene phthalate/adipate, or a mixture of two or more of the above.

The molecular weight of the polyester is preferably a molecular weight in a sheet-forming range. Specifically, it is preferable to use a phenol/tetrachloroethane mixed solvent as the solvent to measure the intrinsic viscosity (IV) of 0.5 or more, and the most ideal range is 0.6 to 1.5, and the formability, mechanical properties, and heat resistance are all good. .

Polyester may contain one or more modified resin components such as vinyl polymers, thermoplastic elastomers, polyarylate resins, and polycarbonates. The amount of the modified resin component is generally less than 50 parts by weight, preferably 5-35 parts by weight, per 100 parts by weight of polyester.

In addition, known compounding agents for plastics, such as oxidation inhibitors, heat stabilizers, ultraviolet absorbers, antistatic agents, fillers, colorants, etc., can also be added. For the purpose of making the container opaque, fillers such as calcium carbonate, calcium silicate, alumina, silicon dioxide, various clays, plaster of paris, talc, magnesium oxide, titanium dioxide, iron oxide yellow, and iron oxide red can be added. , ultramarine blue, chromium oxide and other inorganic or organic pigments.

The thermoplastic resin sheet may have a gas barrier resin layer, a recycled polyester resin layer, an oxygen-absorbing resin layer, etc. as a resin layer other than the polyester layer in order to impart various properties to the manufactured container.

Other resin layers can be used as the inner layer or outer layer in the two-layer structure, and can also be used as the middle layer in the three-layer structure.

The thickness of the thermoplastic resin sheet varies depending on the size of the container, but is generally 0.5 to 5 mm, preferably 1 to 3 mm, which is better in terms of strength and formability of the container.

The container prepared by the manufacturing method of the present invention has a thick-walled bottom, and the container has good independence and independent stability. Moreover, since the area draw ratio is also appropriate, it is excellent in transparency, impact resistance, and heat resistance.

In addition, the flange portion is crystallized by orientation, the formability is improved, and the warpage is improved.

Example

Examples of the present invention are shown below.

Example 1

The cup-shaped container was produced by the method described in the above embodiment. As the thermoplastic resin sheet, an amorphous polyethylene terephthalate sheet (Mitsui Chemicals Co., Ltd., product name: SA135) with a thickness of 1.2 mm and a glass transition temperature of 75° C. was used, and silicone oil ( Shin-Etsu Silicon Co., Ltd., product name: KM-871P).

Manufactured under the molding conditions shown below.

The outer diameter of the male mold: 67mm, the height of the male mold: 108mm,

Flange clamping surface outer diameter: 75mm, pre-clamping clamping surface inner diameter: 94mm,

Sectional shape of pre-clamping clamping surface: plane (width 1mm).

Dimensions of the lower metal mold: adjust to the gap between the male mold and each part is about 1mm.

Sheet temperature: about 95°C, male mold temperature: about 90°C,

Upper metal mold temperature: about 130°C, lower metal mold temperature: about 160°C,

Upper and lower pre-clamping metal mold temperature: about 30 ℃,

Compressed air conditions during thermoforming process and shaping: 0.6MPa,

Insertion amount of the male die (preform amount) at the time of the first stretching: 23 mm.

The shape of the prepared cup-shaped container: the inner diameter of the opening (D) 67mm, the height (H) 108mm,

H/D=1.6, the shape of the flange part is 75mm, the wall thickness of the bottom is 0.28mm,

Bottom area stretch ratio: 4.3 times.

In order to confirm the effects of the present invention, evaluations described later were performed. The results are shown in Table 1.

Under these molding conditions, a good cup-shaped container having a thicker bottom and no warping of the flange was obtained. Furthermore, by pre-clamping, no variation in wall thickness in the circumferential direction at the side wall of the container or the like was found.

(evaluation item)

1) While measuring the wall thickness of the bottom of the container, it is visually evaluated whether or not it is roughly formed into the shape of the male mold.

2) The transparency of the whole container, especially the bottom, was evaluated visually.

3) The warping of the flange portion was confirmed visually, and the flatness of the horizontal surface forming the heat seal was evaluated to be good with a heat seal cap.

4) With regard to the side wall under the flange portion, the appearance conditions such as the presence or absence of scratches and the presence or absence of resin accumulation were evaluated.

5) Put the cup into an incubator whose temperature is adjusted to 100°C. After the surface temperature of the cup reaches 100°C, place it for 10 seconds, and then take it out from the incubator. The heat resistance was evaluated from the rate of change in the amount of filled contents obtained before and after heat treatment according to the following formula. In this evaluation, the heat resistance was generally judged to be good when the rate of change was 2% or less.

Example 2

Without pre-clamping, the insertion amount of the male mold during the first stretching was 15 mm, and the other conditions were the same as in Example 1 to prepare a cup-shaped container. The same evaluation as in Example 1 was performed, and the results are shown in Table 1.

Under these molding conditions, a good cup-shaped container was obtained similarly to Example 1.

Example 3

No silicone oil was applied to the portion corresponding to the flange, and a cup-shaped container was produced under the same conditions as in Example 1 otherwise. The same evaluation as in Example 1 was performed, and the results are shown in Table 1.

Under this molding condition, scratch-like minute scratches were observed on the outer surface of the side wall under the flange portion, and the other conditions were good.

Example 4

The height of the male mold is 90mm, adjust the size of the lower metal mold so that the gap between the lower metal mold and the male mold is about 1mm, the H/D (container height/opening diameter) is 1.3, and the insertion amount of the male mold during the first stretch is 5mm, make a cup-shaped container under the same conditions as in Example 1. The same evaluation as in Example 1 was performed, and the results are shown in Table 1.

Under these molding conditions, a good cup-shaped container as in Example 1 was obtained.

Example 5

The height of the male mold is 145mm, adjust the size of the lower metal mold to the gap between the male mold and each part is about 1mm, H/D is 2.1, the insertion amount of the male mold during the first stretch is 45mm, and the pre-clamping clamping surface Inner diameter is 120mm, makes cup-shaped container under other conditions identical with embodiment 1. The same evaluation as in Example 1 was performed, and the results are shown in Table 1.

Under these molding conditions, a good cup-shaped container as in Example 1 was obtained.

Example 6

The insertion amount of the male die during the first stretching was 31 mm, and a cup-shaped container was produced under the same conditions as in Example 1 otherwise. The same evaluation as in Example 1 was performed, and the results are shown in Table 1.

Under these molding conditions, a good cup-shaped container as in Example 1 was obtained.

Example 7

The insertion amount of the male die during the first stretching was 5.4 mm, and a cup-shaped container was produced under the same conditions as in Example 1 otherwise. The same evaluation as in Example 1 was performed, and the results are shown in Table 1.

Under these molding conditions, a good cup-shaped container as in Example 1 was obtained.

Comparative example 1

The preforming process was omitted, and a cup-shaped container was prepared under the same conditions as in Example 1. At this time, no pre-clamping effect in the sense of preventing resin entanglement between the metal molds was found. Table 1 shows the results of the same evaluation as in Example 1 for the obtained container.

Under this molding condition, the flange portion is warped upward, and resin stagnation occurs inside the flange. Moreover, the draw ratio at the bottom is high, and the wall thickness becomes thinner.

Industrial Utilization Possibility

The present invention can provide a method for manufacturing a thermoplastic resin container that has a thickened container bottom and improved warpage of the flange.

Claims (14)

1. the manufacture method of a thermoplastic resin container is with the method for formpiston from thermoplastic resin thin slice heating shaping cup-like containers, it is characterized in that,

Utilizing after pre-clamping metal pattern fixes the forming section periphery of above-mentioned thermoplastic resin thin slice, above-mentioned thermoplastic resin thin slice is carried out preform by above-mentioned formpiston;

Then, preform part with above-mentioned thermoplastic resin thin slice, to be undertaken after the stretch forming by above-mentioned formpiston by the state of last metal pattern and following metal pattern clamping, compressed air is configured as the above above-mentioned interior shape of metal pattern down of crystallized temperature that is heated to above-mentioned thermoplastic resin thin slice, carries out heat fixation simultaneously;

Then, decompression in the formed body is made it to shrink, figuration is the shape as the above-mentioned formpiston of final container shape, cools off simultaneously.

2. the manufacture method of thermoplastic resin container as claimed in claim 1 is characterized in that, the temperature of described pre-clamping metal pattern is cooled to below the glass transition temperature of above-mentioned thermoplastic resin thin slice or below the softening point.

3. the manufacture method of thermoplastic resin container as claimed in claim 1 is characterized in that, described preform is that the part corresponding with the peristome of above-mentioned cup-like containers or flange part stretched.

4. the manufacture method of thermoplastic resin container as claimed in claim 2 is characterized in that, described preform is that the part corresponding with the peristome of above-mentioned cup-like containers or flange part stretched.

5. the manufacture method of thermoplastic resin container as claimed in claim 3 is characterized in that, when carrying out described clamping, extruding with a part of resin of above-mentioned flange part counterpart week and peripheral direction in flange, above-mentioned flange part simultaneously is shaped.

6. the manufacture method of thermoplastic resin container as claimed in claim 4 is characterized in that, when carrying out described clamping, extruding with a part of resin of above-mentioned flange part counterpart week and peripheral direction in flange, above-mentioned flange part simultaneously is shaped.

7. the manufacture method of thermoplastic resin container as claimed in claim 3 is characterized in that, described thermoplastic resin thin slice is application of lubricating on corresponding to the part of above-mentioned flange part at least.

8. the manufacture method of thermoplastic resin container as claimed in claim 4 is characterized in that, described thermoplastic resin thin slice is application of lubricating on corresponding to the part of above-mentioned flange part at least.

9. the manufacture method of thermoplastic resin container as claimed in claim 5 is characterized in that, described thermoplastic resin thin slice is application of lubricating on corresponding to the part of above-mentioned flange part at least.

10. the manufacture method of thermoplastic resin container as claimed in claim 6 is characterized in that, described thermoplastic resin thin slice is application of lubricating on corresponding to the part of above-mentioned flange part at least.

11. the manufacture method of thermoplastic resin container as claimed in claim 1 or 2 is characterized in that, described thermoplastic resin thin slice is made up of thermoplastic polyester at least.

12. the manufacture method of thermoplastic resin container as claimed in claim 1 or 2, it is characterized in that, described pre-clamping metal pattern, be provided with the last pre-clamping metal pattern that is arranged at the above-mentioned periphery that goes up metal pattern coaxially and be arranged at the above-mentioned following pre-clamping metal pattern of the periphery of metal pattern down coaxially, and on above-mentioned the above-mentioned thermoplastic resin thin slice of clamping on every side of metal pattern and above-mentioned metal pattern down.

13. the manufacture method of thermoplastic resin container as claimed in claim 1 or 2 is characterized in that, is 1.3～2.1 to form with the height H/peristome diameter D of described thermoplastic resin container.

14. the manufacture method of thermoplastic resin container as claimed in claim 1 or 2 is characterized in that, the area stretching ratio bottom described thermoplastic resin container is 3.5～10 times and forms.

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